I got stuck at level 14 and when I looked up a walkthrough, it turned out the method doesn't work in the webplayer. It also seams like there are 5 other levels that have been removed. The method is to stack two guys on top of each other, let the bottom one jump, switch to the guy on top and have him jump at nearly the same time. Though I did really enjoy the puzzles in the other levels and good job on the fact that you couldn't progress untill you had figured out the new method required to complete each level.
Level 14 is possible in the webplayer. I just created a short video for it here:
Alright thank you, but isn't it kind of odd that the solution in the walkthrough doesn't work in the webplayer? I tried it again and your method is really hard to pull of (so unlikely the intended solution). I found that if you stack two guys on top of each other and quickly press the up key mutliple times, the stack of them moves up indefinitely.